1. Field of the Invention
This invention relates to a combustion device of a kerosene fan heater, which can inhibit accumulation of tar inside of the carburetor and can improve a mixing efficiency of fuel of kerosene and air.
2. Description of the Prior Art
In general, a kerosene fan heater, being a heater heating a room with a heat generated on combustion of vaporized fuel of kerosene, includes, as shown in FIG. 1, a fuel feeding device for feeding fuel, a combustion device for vaporizing and burning the fuel fed thereto by the fuel feeding device, and an air supply device for supplying air to the combustion device.
Explained in detail, the fuel feeding device includes a fuel feeding pipe 3 for guiding fuel fed from a cartridge tank through a oil metering tank 2, an electronic pump 4 connected to the fuel feeding pipe for pumping fuel fed through the fuel feeding pipe 3, a constant leveller 5 for maintaining a constant level of fuel pumped by the electronic pump, and a pipe orifice 6 provided inside of the constant leveller for guiding fuel to the combustion device.
And the combustion device includes an air supply passage 7 for guiding air supplied by the air supply device, a solenoid 9 mounted on the air supply passage for opening/closing supply of air to the constant leveller 5 of the fuel feeding device through a pressurizing tube 8, a nozzle 10 connected to the end of the air supply passage 7 for blowing air, a needle 11 connected to the end of the pipe orifice 6 of the fuel feeding device inserted in the nozzle for injecting fuel laden on air blowing from the nozzle 10, a carburetor 12 connected to the end of the nozzle 10 for vaporizing the fuel injected laden on air, a preheater 13 provided around the wall of the carburetor buried therein for preheating the carburetor 12, a preheat sensing thermistor 14 provided at the bottom of the carburetor 12 for sensing preheat temperature of the carburetor 12 preheated by the preheater 13, an ignition plug 15 for flying spark to the fuel gas vaporized in the carburetor preheated by the preheater 13, a burner head 16 covering top of the carburetor for burning fuel gas ignited by the ignition plug 15, a flame detector for detecting flame formed at the burner head, and a cooling jacket 19 formed surrounding the carburetor 12 for cooling the carburetor 12 with air supplied from the air supply passage 7 through a cooling tube 18.
In order to vaporize the fuel injected into the carburetor 12 laden on the blowing air, the fuel injected laden on the air should be made to swirl along inner wall of the carburetor 12, for which the end of the nozzle 10 is connected to the carburetor tangential to the inner wall of the carburetor 12.
And the air supply device includes a blower 20 for drawing in air form outside and blowing the air to the air supply passage 7 of the combustion device, and a filter 21 for filtering foreign particles from the air drawn in by the blower.
Accordingly, when the cartridge tank 1 filled with fuel is placed on the metering tank 2 of the fuel feeding device, the fuel filled in the cartridge tank i flows down into the metering tank 2 and stored therein.
Under the above condition, when a user turns on a power switch, a control part(not shown) controls the preheater 13 buried around the carburetor 12 to preheat the carburetor 12, and when the temperature sensed at the preheat sensing thermistor 14 of the carburetor is reached to a preset value, the control part stops preheating of the carburetor 12 and, on the same time, operates the blower 20 of the air supply part 20 and the electronic pump 4 of the fuel feeding device.
The operated blower 20 blows air cleared of various foreign particles through the filter 21, only through the air supply passage 7 and the nozzle 10 into the carburetor 12 for 20-30 seconds before ignition for cleaning inside of the carburetor 12, and the operated electronic pump 4 feeds the fuel from the metering tank 2 through the fuel feed pipe 3 to the constant leveller 5 that maintains a constant level of the fuel thereof.
In this time, the fuel maintaining a constant level in the constant leveller is, pressurized by a part of the air from the air supply passage 7 entered into the constant leveller 5 by continuous guide of the pressurizing tube 8 at opening of the solenoid 9 operated in response to a control signal of the control part, flows through the needle 11 guided by the pipe orifice 6, primarily atomized by and laden on the air blowing through the nozzle 10 into inside of the carburetor 12 even after the above 20-30 seconds of blowing for cleaning inside of the carburetor 12, fed into inside of the preheated carburetor 12.
And the fuel sprayed into the preheated carburetor 12 laden on air, swirls along the inner wall of the carburetor due to the tangential connection of the nozzle 10 to the inner wall of the carburetor, vaporizes into vaporized fuel gas by the heat of inner wall of the preheated carburetor 12, further mixes with air while swirling, and exhausts through the burner head 16 covering top of the carburetor when the fuel gas is ignited by the spark flying from the ignition plug 15 to form flame.
When the flame detector 17 detects formation of flame at ignition of fuel gas in initial stage of ignition and applies the signal on detection of flame, the control part, discriminates abnormal conditions of the applied flame detection signal, and if there are no abnormal conditions found, checks other safety devices, and controls to carry out a normal room heating.
However, since the conventional combustion device of a kerosene fan heater has a construction that makes the fuel fed into the carburetor through the needle laden on the air blowing through the nozzle vaporize as it swirls along the inner wall of the carburetor in one direction after it impinges onto the inner wall directly, the combustion device has following problems.
First, since the fuel that has not been vaporized on impinging at the inner wall of the carburetor vaporizes as it flows down from the wall to the bottom while forming oil film on the wall and the bottom, cooled part is concentrated at the wall and the bottom of the carburetor, causing a non-uniform difference of temperature distribution of 60 to 70 deg. C. for entire part of the carburetor, there has been a problem of safety at operation of the combustion device.
Second, since tar is formed at the bottom of the carburetor due to continuous formation of oil film on the concentrated cooled part where fuel can not vaporize instantaneously, and the tar once formed forms tar nuclei which deteriorates a heat transfer characteristic of the carburetor, causing excessive emission of unburned gas at ignition due to defective ignition and at extinction due to residual fuel inside of the tar as shown in FIGS. 6a and 6b, the room air becomes polluted with bad smell.
Third, the combustion noise is large and the combustion efficiency is low due to instability of flame because the vaporized fuel gas burns while exhausting through the burner head, under a condition that the vaporized fuel gas has not been mixed sufficiently with air through swirling within the carburetor since the swirling moment of the fuel injected into the carburetor laden on air blowing through the nozzle is weakened at impinging onto the inner wall of the carburetor.